The irony is that, when the account on the Windows laptop is configured to have a password, and the correct password is entered, the connection works.

In theory, it should work in both cases: if there's no password, and no password is entered, there should be no reason to deny access. So, why doesn't it work? Does Samba consider "empty password" as a special case?

Note that this effectively strips any protection you can have against attackers from modifying your shared files. I would recommend to actually set up a password and add to the fstab an automount entry with the password saved.